Preliminary studies concerning age were carried out on a Maryland Cancer Society Grant, but more animals need to be included. These studies showed that younger animals were more susceptible than older animals. It is proposed that the following ages be studied: 4 day, 1 week, 5 week, 12 week, 24 week, 36 week, and 52 week. (14 groups of rats). Buffalo male rats are more susceptible than female rats to the development of carcinomas of the large bowel by MAM acetate. It is proposed in include studies on: (a) castrated male rats; (b) castrated females rats; (c) castrated female rats given testosterone porpionate; and (d) castrated male rats given diethylstilbestrol (8 groups of rats).